[MPlayer-dev-eng] [PATCH 6/12] ao_alsa: use more OSS-compatible behaviour

[Clemens Ladisch]

This changes the software parameters to be more compatible with the
behaviour of the OSS driver.  This implies that underruns are not longer
reported.

Index: MPlayer-1.0pre7try2/libao2/ao_alsa.c
===================================================================
--- MPlayer-1.0pre7try2.orig/libao2/ao_alsa.c	2006-02-05 22:52:13.000000000 +0100
+++ MPlayer-1.0pre7try2/libao2/ao_alsa.c	2006-02-05 22:52:14.000000000 +0100
@@ -264,6 +264,7 @@ static int init(int rate_hz, int channel
     int block;
     strarg_t device;
     snd_pcm_uframes_t bufsize;
+    snd_pcm_uframes_t boundary;
     opt_t subopts[] = {
       {"mmap", OPT_ARG_BOOL, &ao_mmap, NULL},
       {"block", OPT_ARG_BOOL, &block, NULL},
@@ -289,7 +290,6 @@ static int init(int rate_hz, int channel
     ao_data.samplerate = rate_hz;
     ao_data.format = format;
     ao_data.channels = channels;
-    ao_data.outburst = OUTBURST;
 
     switch (format)
       {
@@ -607,6 +607,49 @@ static int init(int rate_hz, int channel
 	  mp_msg(MSGT_AO,MSGL_V,"alsa-init: got buffersize=%i\n", ao_data.buffersize);
       }
 
+      if ((err = snd_pcm_hw_params_get_period_size(alsa_hwparams, &chunk_size, NULL)) < 0) {
+	mp_msg(MSGT_AO,MSGL_ERR,"alsa-init: unable to get period size: %s\n", snd_strerror(err));
+      } else {
+	mp_msg(MSGT_AO,MSGL_V,"alsa-init: got period size %li\n", chunk_size);
+      }
+      ao_data.outburst = chunk_size * bytes_per_sample;
+
+      /* setting software parameters */
+      if ((err = snd_pcm_sw_params_current(alsa_handler, alsa_swparams)) < 0) {
+	mp_msg(MSGT_AO,MSGL_ERR,"alsa-init: unable to get sw-parameters: %s\n",
+	       snd_strerror(err));
+	return 0;
+      }
+      if ((err = snd_pcm_sw_params_get_boundary(alsa_swparams, &boundary)) < 0) {
+	mp_msg(MSGT_AO,MSGL_ERR,"alsa-init: unable to get boundary: %s\n",
+	       snd_strerror(err));
+	return 0;
+      }
+      /* start playing when one period has been written */
+      if ((err = snd_pcm_sw_params_set_start_threshold(alsa_handler, alsa_swparams, chunk_size)) < 0) {
+	mp_msg(MSGT_AO,MSGL_ERR,"alsa-init: unable to set start threshold: %s\n",
+	       snd_strerror(err));
+	return 0;
+      }
+      /* disable underrun reporting */
+      if ((err = snd_pcm_sw_params_set_stop_threshold(alsa_handler, alsa_swparams, boundary)) < 0) {
+	mp_msg(MSGT_AO,MSGL_ERR,"alsa-init: unable to set stop threshold: %s\n",
+	       snd_strerror(err));
+	return 0;
+      }
+      /* play silence when there is an underrun */
+      if ((err = snd_pcm_sw_params_set_silence_size(alsa_handler, alsa_swparams, boundary)) < 0) {
+	mp_msg(MSGT_AO,MSGL_ERR,"alsa-init: unable to set silence size: %s\n",
+	       snd_strerror(err));
+	return 0;
+      }
+      if ((err = snd_pcm_sw_params(alsa_handler, alsa_swparams)) < 0) {
+	mp_msg(MSGT_AO,MSGL_ERR,"alsa-init: unable to set sw-parameters: %s\n",
+	       snd_strerror(err));
+	return 0;
+      }
+      /* end setting sw-params */
+
       if ((err = snd_pcm_prepare(alsa_handler)) < 0)
 	{
 	  mp_msg(MSGT_AO,MSGL_ERR,"alsa-init: pcm prepare error: %s\n", snd_strerror(err));
@@ -723,37 +766,6 @@ do { \
 } while (0)
 #endif
 
-/* I/O error handler */
-static int xrun(u_char *str_mode)
-{
-  int err;
-  snd_pcm_status_t *status;
-
-  snd_pcm_status_alloca(&status);
-  
-  if ((err = snd_pcm_status(alsa_handler, status))<0) {
-    mp_msg(MSGT_AO,MSGL_ERR,"status error: %s", snd_strerror(err));
-    return(0);
-  }
-
-  if (snd_pcm_status_get_state(status) == SND_PCM_STATE_XRUN) {
-    struct timeval now, diff, tstamp;
-    gettimeofday(&now, 0);
-    snd_pcm_status_get_trigger_tstamp(status, &tstamp);
-    timersub(&now, &tstamp, &diff);
-    mp_msg(MSGT_AO,MSGL_INFO,"alsa-%s: xrun of at least %.3f msecs. resetting stream\n",
-	   str_mode,
-	   diff.tv_sec * 1000 + diff.tv_usec / 1000.0);
-  }
-
-  if ((err = snd_pcm_prepare(alsa_handler))<0) {
-    mp_msg(MSGT_AO,MSGL_ERR,"xrun: prepare error: %s", snd_strerror(err));
-    return(0);
-  }
-
-  return(1); /* ok, data should be accepted again */
-}
-
 /*
     plays 'len' bytes of 'data'
     returns: number of bytes played
@@ -780,13 +792,7 @@ static int play(void* data, int len, int
 
     res = snd_pcm_writei(alsa_handler, (void *)output_samples, num_frames);
 
-      if (res == -EPIPE) {  /* underrun */
-	if (xrun("play") <= 0) {
-	  mp_msg(MSGT_AO,MSGL_ERR,"alsa-play: xrun reset error");
-	  return(0);
-	}
-      }
-      else if (res == -ESTRPIPE) {	/* suspend */
+      if (res == -ESTRPIPE) {	/* suspend */
 	mp_msg(MSGT_AO,MSGL_INFO,"alsa-play: pcm in suspend mode. trying to resume\n");
 	while ((res = snd_pcm_resume(alsa_handler)) == -EAGAIN)
 	  sleep(1);